Marine ecosystem
Marine ecosystems encompass the diverse communities of living organisms and their environments found in the world's oceans, which cover about 71% of the Earth's surface. These ecosystems vary significantly in structure and function, ranging from the dark depths of the deep sea, where life thrives despite extreme conditions, to vibrant coral reefs that support a myriad of species. Deep sea organisms have adapted to high pressure and lack of light, relying on hydrothermal vents for warmth and food. Coral reefs, primarily found in warm tropical waters, are not only beautiful structures built by coral organisms but also vital habitats for countless marine species, creating mutually beneficial relationships within their complex ecosystem.
Kelp forests represent another essential marine ecosystem, where large sea plants provide shelter and sustenance for various marine life, similar to terrestrial forests. The Arctic Ocean, with its unique and frigid conditions, supports life through specialized adaptations, forming a structured food chain that sustains its biodiversity even in extreme environments. Overall, marine ecosystems are critical for global biodiversity and have yet to reveal many of their secrets, with scientists estimating that a significant number of species remain undiscovered. Understanding these ecosystems is vital for appreciating the complexity of ocean life and the ecological balance they maintain.
Marine ecosystem
Earth's combined oceans cover about 71 percent of the planet's surface. Although most oceans look identical on their surfaces, their true diversity is displayed under their waters. Here, numerous varieties of marine ecosystems thrive. An ecosystem consists of all the living and nonliving things in a particular area. The oceans have long been home to a great range of ecosystems.
The Deep Sea
Scientists today know little about the ocean's farthest depths. This is because it is difficult to explore a cold, dark area that is under so much water pressure, which is the weight of all the water above a certain point. Despite these apparent challenges to life, the deep sea is actually a diverse and biologically flourishing marine ecosystem.
Located miles below the ocean surface, the deep sea lies well out of range of the photic zone, the several hundred feet of water that sunlight can reach. Many species of fish have adapted to living in these areas of extreme cold and utter darkness. For heat, they rely on hydrothermal vents, openings in the ocean floor that emit heat from Earth's interior. Fish that live in areas where some faint light is still visible may have developed large eyes so they can see as much as possible. In some completely dark regions, the fish have no eyes. They rely on their other senses to navigate.
Food is scarce in this ocean abyss. The fish there have adapted to be able to eat any organism they encounter, even larger ones. They do this by unhinging their wide jaws to attack and eat fish of almost any size. For defense, some fish emit faint lights from their bodies to confuse or intimidate predators. In these ways, the organisms, or living things, of this deep ocean ecosystem have learned to survive.
Coral Reefs
Coral reefs are large, colorful underwater structures made of corals. These are hard, scaly, predatory sea plants that grow on rocks or on the ocean floor. The ends of coral bodies contain stingers called nematocysts, which corals use to catch small fish for nourishment.
Individual corals can grow in a range of temperatures, but reefs exist only in the warm waters of the tropics, where they greatly benefit from the Sun's energy. The world's largest coral reef is the 1,600-mile Great Barrier Reef east of Australia. It has grown so large over the last twenty thousand years that it can even be seen from space.
Although coral reefs can be considered their own ecosystems unto themselves, they also provide homes and feeding grounds for other kinds of marine organisms, many of which defend themselves and the reefs from predators when necessary. For example, shrimp and crabs that live in the protection of coral reefs are sometimes forced to chase away fish, worms, and sea stars that feed on coral. In doing this, the relationship between the coral reefs and the animals they host in their branches becomes mutually beneficial. Despite the great size of some coral reefs, they occupy less than 2 percent of the world's oceans.
Kelp Forests
Another distinct type of marine ecosystem is the kelp forest. Kelp is a large-leaf sea plant that grows in tall stalks from the ocean floor. Because these plants rely on sunlight for survival and growth, they are usually found in shallow parts of the ocean and do not extend more than 130 feet below the water's surface. With enough exposure to the Sun, a stalk of kelp can grow about eighteen inches a day.
Kelp forests are similar to land forests in that the kelp stalks grow together so thickly that, much like trees, their canopies eventually block most or all sunlight from breaking through to the forest floor. Many marine organisms take shelter in the natural protection provided by kelp forests. These organisms include sea otters, seals, and whales, all of which use the forests' large leaves and dark shadows to hide from potential predators.
The Arctic Ocean
The Arctic Ocean is so unlike the warmer Atlantic, Pacific, and Indian Oceans that it can qualify as its own ecosystem. It measures nearly 5.5 million square miles in area and between 12,000 and 17,800 feet in depth. At the North Pole, temperatures are so cold that the Arctic Ocean is usually a frozen sheet of ice. Even when the ice melts in summer, the ocean's waters remain only a few degrees above freezing.
Certain kinds of life can still survive in these extreme conditions. When the ocean freezes again, it often leaves open tunnels called brine channels buried deep in the ice. These channels house a variety of algae and bacteria until the ice melts once again. Once in open water, these organisms sink and become minerals for the underwater algae plant, which is then eaten by small organisms called zooplankton. These zooplankton are then consumed by Arctic sea creatures, such as whales, seals, and squid. Polar bears then stand on ice near the water's edge to catch and eat fish and seals. When winter returns and the Arctic freezes again, this structured food chain—a hierarchy of predators and prey—begins anew. In this way, the marine ecosystem of the Arctic remains self-sustaining.
Continued Life of the Oceans
Many other types of marine ecosystems exist in and near the world's oceans. These include the extensive underwater flatlands of the abyssal plains and the tide pools formed on rocky seashores by ocean surf. Scientists have identified about 250,000 species of marine life, but they believe that close to a million other species have yet to be discovered.
These organisms live in places inaccessible to people, where temperatures are too hot or too cold or where no sunlight can reach. In contemporary oceanography, which has produced everything currently known about marine ecosystems, about 80 percent of ocean life still remains a mystery.
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